Vulnerability scanners can help you automate security auditing and can play a crucial part in your IT security. They can scan your network and websites for up to thousands of different security risks, producing a prioritised list of those you should patch, describe the vulnerabilities, and give steps on how to remediate them. Some can even automate the patching process.
Though vulnerability scanners and security auditing tools can cost a fortune, there are free options as well. Some only look at specific vulnerabilities, but there are also those that offer broad IT security scanning.